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Show 250 CIROUMNUTATION OF LEAVES. CHAP. IV. or exclusively due to the straightening of the blade, and not to the movement of t.hc petiole. We may therefore conclude that the leaves of Acanthus circumnutate periodically, falling in the morning and rising in the afternoon and night. (24.) Oannab£s sa.tiva (Cannahincre, Fam. 195).-We have here the rare case of leaves moving do·wuwards in the evening, but not to fL sufficient degree to be called sleep.* In the e11rly morning, or in tho latter part of the night, they move upwards. For instance, all the young leaves near tho summits of several stems stood alm9st horizontally at 8 A.M. May 29th, and at 10.30 P.M. were considerably declined. On a subsequent day two leaves stc;>od at 2 P.M. at 21° and 12° beneath tho horizon, and at 10 P.M. at 3B0 beneath it. Two other leaves on a younger plant were horizontal at 2 P.M., and at 10 P.M. had sunk to 36° beneath the horizon. With respect to this downward movement of the leaves, Kraus believes that it is duo to their epinastic growth. He adds, that the leaves are relaxed during the day, and tense at night, both in sunny and rainy weather. (25.) Pinus pinaster (Coniferro, Faro. 223).- Tho leaves on the summits of the terminal shoots stand at first in a bundle almost upright, but they soon diverge and ultimately become almost horizontal. The movements of a young loaf, nearly one inch in length, on the summit of a seedling plant only 3 inches high, were traced from the early morning of Juno 2nd to the evening of the 7th. During those five days tho leaf diverged, and its apex descended at first in an almost straight line ; but during the two latter days it zigzagged so much that it was evidently circumnu· tating. The same little plant, when grown to a height of 5 inches, was again observed during four days. A filn.ment was fixed transversely to the apex of a leaf, one inch in length, and which had already diverged considerably from its originally upright position. It continued to diverge (see A, Fig. 113), and to descend from 11.45 A.M. July 31st to 6.40 A.M. Aug. 1st. On August 1st it circumnutated about the same small space, and again descended at night. Next morning the pot was movoo nearly one inch to the right, and a new tracing was begun (B). From this time, viz., 7 A.M. August 2nd to 8.20 A.M. on the 4th, * We were led to observe this plant by Dr. Carl Kraus' paper, 'Beitrage zur Kentniss der Bewegungen Wa.chsonder Laubblatter,' Flora, 1879, p. G6. We regret th~t we co.n not fully understand par 8 of this puper. CHAP. IV. DICOTYLEDONS. 251 th.e leaf manifestly circumnutated · It doe-s n ot appear fr om the diagram that the leaves move periodically ., . th d d' d . , tOI e escen mg course urmg the first two nights' was cleai·l Y d uo to epm. astl.c 11"45'a.m. :u~t 6°410' a.m:J.'.l i t I I I ! ! I i I A. Fig. 113, B. PinuJsu lpyi n3a1sstat rt o' c8i r2c0u ~n:tatJ.O n of young leaf, tmced from 11 .4il .A.M. moved an inch to o . ·. Aug. 4th. At 7 ~.M. Aug. 2nd the pot was Apex of leaf 14~ . n\s!de, so that the t.raclllg consists of two figures. magnified. mc es from the vertical glass, so movements much ngeroawrlyth s, oa.bn d .a t the cI o~e of our observations the leaf was not Pinu onz?ntal as 1t would ultimately become. 8 austnaca ·- T wo 1e aves, a. m. ches m. length, but not |